Out of interest, I decided to remain subscribed to the old feed to see what, if anything happened about it. And this morning in Bloglines I a message in the old feed, inviting people to move to the new one.
Obviously it would have been nicer if there was just a redirect from old to new, but that would have needed some technical resource, where as popping a message in the old feed is no doubt something that the production team could do with relative ease. Yes I know the technical work would be extremely easy but I also know from my time in the BBC that getting the really quick and easy stuff done is often ridiculously hard! And the main thing ultimately is that users are told of the changes some how or other - rather than just finding the feed stops forever, or (far worse, and occuring more often), the feed just suddenly 404s.
Like about 20,000 I was subscribed to an unofficial feed to get my daily dose of Dilbert, and had been for years. In a way I'm surprised the unofficial one was tolerated for so long, but it's very good to see that the Dilbert web team decided that it was better to do it themselves!